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Direct laying method of laying┬а underground cable has drawback of
High maintenance cost
Localization of fault difficulty
Possibility of damage of cable sheath owning to undergoing chemical changes due to impurities present in the soil
All of above
Localization of fault difficulty
The direct laying method, also known as the trench laying method, involves burying cables directly in the ground. While economical for simple layouts, it suffers from several critical drawbacks, including susceptibility to chemical corrosion from soil impurities, difficulty in locating faults, and higher maintenance costs associated with excavation for repairs.
The direct laying method, also known as the trench laying method, involves burying cables directly in the ground. While economical for simple layouts, it suffers from several critical drawbacks, including susceptibility to chemical corrosion from soil impurities, difficulty in locating faults, and higher maintenance costs associated with excavation for repairs.
RcтАЛ=╧БAlтАЛ тАФ Resistance formula relating to cable length l and area A, where corrosion increases ╧Б (resistivity) over time due to sheath degradation.
In direct laying, the cable is placed in a trench of depth 0.5 to 1.2 meters, covered with sand, and then protected with bricks or tiles. Since the cable is in direct contact with the surrounding earth, any acidic or alkaline impurities in the soil can react with the metallic sheath (e.g., lead), leading to corrosion. Furthermore, because the cable is buried, pinpointing a specific fault requires excavation along the route, which is labor-intensive and costly.
Direct laying is the most economical method for underground cable installation.
Soil chemistry (pH levels, moisture, sulfates) significantly impacts the life of the metallic sheath.
Fault localization requires complex equipment like a Murray Loop bridge or Radar-based Time Domain Reflectometry (TDR).
Maintenance is expensive as it requires digging up the earth, causing public inconvenience.
Simple and low initial installation cost
Good heat dissipation due to direct contact with the ground
Difficult to detect fault locations
High risk of chemical corrosion
Costly maintenance due to excavation
Not suitable for crowded urban areas
Rural areas with low population density
Long-distance transmission where land is available
The standard depth for laying 11kV cables is typically 0.9m to 1.0m to avoid mechanical damage.
Option B is correct as the lack of visual access makes fault location extremely challenging compared to duct systems.
D is correct тАФ The direct laying method is burdened by environmental corrosion risks, inherent difficulty in fault detection, and the high financial/labor costs of excavation during maintenance.
Always remember that while direct laying has the lowest initial capital expenditure, it incurs the highest operational expenditure (OPEX) in terms of maintenance and fault diagnostics.